Active memory command engine and method

ABSTRACT

A command engine for an active memory receives high level tasks from a host and generates corresponding sets of either DCU commands to a DRAM control unit or ACU commands to a processing array control unit. The DCU commands include memory addresses, which are also generated by the command engine, and the ACU command include instruction memory addresses corresponding to an address in an array control unit where processing array instructions are stored.

TECHNICAL FIELD

The invention relates memory devices, and, more particularly, to asystem and method for internally supplying processing element commandsand memory device commands in an active memory device.

BACKGROUND OF THE INVENTION

A common computer processing task involves sequentially processing largenumbers of data items, such as data corresponding to each of a largenumber of pixels in an array. Processing data in this manner normallyrequires fetching each item of data from a memory device, performing amathematical or logical calculation on that data, and then returning theprocessed data to the memory device. Performing such processing tasks athigh speed is greatly facilitated by a high data bandwidth between theprocessor and the memory devices. The data bandwidth between a processorand a memory device is proportional to the width of a data path betweenthe processor and the memory device and the frequency at which the dataare clocked between the processor and the memory device. Therefore,increasing either of these parameters will increase the data bandwidthbetween the processor and memory device, and hence the rate at whichdata can be processed.

A memory device having its own processing resource is known as an activememory. Conventional active memory devices have been provided formainframe computers in the form of discrete memory devices provided withdedicated processing resources. However, it is now possible to fabricatea memory device, particularly a dynamic random access memory (“DRAM”)device, and one or more processors on a single integrated circuit chip.Single chip active memories have several advantageous properties. First,the data path between the DRAM device and the processor can be made verywide to provide a high data bandwidth between the DRAM device and theprocessor. In contrast, the data path between a discrete DRAM device anda processor is normally limited by constraints on the size of externaldata buses. Further, because the DRAM device and the processor are onthe same chip, the speed at which data can be clocked between the DRAMdevice and the processor can be relatively high, which also maximizesdata bandwidth. The cost of an active memory fabricated on a single chipcan is also less than the cost of a discrete memory device coupled to anexternal processor.

Although a wide data path can provide significant benefits, actuallyrealizing these benefits requires that the processing bandwidth of theprocessor be high enough to keep up with the high bandwidth of the widedata path. One technique for rapidly processing data provided through awide data path is to perform parallel processing of the data. Forexample, the data can be processed by a large number of processingelements (“PEs”) each of which processes a respective group of the databits. One type of parallel processor is known as a single instruction,multiple data (“SIMD”) processor. In a SIMD processor, each of a largenumber of PEs simultaneously receive the same instructions, but theyeach process separate data. The instructions are generally provided tothe PE's by a suitable device, such as a microprocessor. The advantagesof SIMD processing are that SIMD processing has simple control,efficiently uses available data bandwidth, and requires minimal logichardware overhead.

An active memory device can be implemented by fabricating a large numberof SIMD PEs and a DRAM on a single chip, and coupling each of the PEs torespective groups of columns of the DRAM. The instructions are providedto the PEs from an external device, such as a microprocessor. The numberof PE's included on the chip can be very large, thereby resulting in amassively parallel processor capable of processing vast amounts of data.However, this capability can be achieved only by providing instructionsto the PEs at a rate that is fast enough to allow them to operate attheir maximum speed. It can require more time to couple instructions tothe PEs from an external device, such as a microprocessor, than the timerequired to execute the instructions. Under these circumstances, the PEswill be operating at less than their maximum processing speed.

There is therefore a need for a system and method for more rapidlyproviding instructions to SIMD PE's that are embedded in a DRAM.

SUMMARY OF THE INVENTION

An integrated circuit active memory device is preferably fabricated on asingle semiconductor substrate. The active memory device includes amemory device coupled to an array of processing elements through a databus having a plurality of data bus bits. Each processing elements arepreferably coupled to a respective group of the data bus bits, and eachof the processing elements have an instruction input coupled to receiveprocessing element instructions for controlling the operation of theprocessing elements. The processing element instructions are provided byan array control unit, and memory device instructions for controllingthe operation of the memory device are provided by a memory devicecontrol unit. The array control unit is coupled to the processingelements in the array, and it is operable to generate and to couple theprocessing element instructions to the processing elements. Each of aplurality of sets of processing element instructions are generatedresponsive to a respective one of a plurality; of array control unitcommands applied to a command input of the array control unit. A memorycontrol unit coupled to the memory device is operable to generate and tocouple respective sets of memory commands to the memory deviceresponsive to each of a plurality of memory control unit commandsapplied to a command input of the memory control unit. Respective setsof the array control unit commands and respective sets of the memorycontrol unit commands are provided by a command engine responsive torespective task commands applied to a task command input of the commandengine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an active memory device according to oneembodiment of the invention.

FIG. 2 is a block diagram of a command engine used in the active memorydevice of FIG. 1.

FIG. 3 is a block and logic diagram of the command engine of FIG. 2according to one embodiment of the invention.

FIG. 4 is a block diagram of a computer system using the command engineof FIG. 1 according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an active memory device 10 according to one embodiment ofthe invention. The memory device 10 is coupled to a host 14, such as amicroprocessor, although it may be coupled to other devices that supplyhigh-level instructions to the memory device 10. The memory device 10includes a first in, first out (“FIFO”) buffer 18 that receives highlevel tasks from the host 14. Each task includes a task command and mayinclude a task address, The received task commands are buffered by theFIFO buffer 18 and passed to a command engine unit 20 at the proper timeand in the order in which they are received. The command engine unit 20generates respective sequences of commands corresponding to receivedtask commands. As described in greater detail below, the commands are ata lower level than the task commands received by the command engine unit20. The commands are coupled from the command engine unit 20 to either aprocessing element (“PE”) FIFO buffer 24 or a dynamic random accessmemory (“DRAM”) FIFO buffer 28 depending upon whether the commands arePE commands or DRAM commands. If the commands are PE commands, theypassed to the PE FIFO buffer 24 and then from the FIFO buffer 24 to aprocessing array control unit (“ACU”) 30. If the commands are DRAMcommands, they are passed to the DRAM FIFO buffer 28 and then to a DRAMControl Unit (“DCU”) 34.

As explained in greater detail below, the ACU 30 executes an intrinsicroutine containing several instructions responsive to the command fromthe FIFO buffer 24, and these instructions are executed by an array ofPEs 40. The PE's operate as SIMD processors in which all of the PEs 40receive and simultaneously execute the same instructions, but they do soon different data or operands. In the embodiment shown in FIG. 1, thereare 256 PE's 40 each of which is coupled to receive 8 bits of data fromthe DRAM 44 through register files 46. In the embodiment shown in FIG.1, the DRAM 44 stores 16M bytes of data. However, it should beunderstood that the number of PEs used in the active memory device 10can be greater or lesser than 256, and the storage capacity of the DRAM44 can be greater or lesser than 16 Mbytes.

Different intrinsic routines containing different instructions areissued by the ACU 30 for different commands received from the FIFObuffer 24. As also explained below, the DCU 34 issues memory commandsand addresses responsive to commands from the DRAM FIFO buffer 34. Inresponse, data are either read from a DRAM 44 and transferred to theregister files 46, or written to the DRAM 44 from the register files 46.The register files 46 are also available to the PE's 40. The ACU 30 andthe DCU 34 are coupled to each other so the operation of each of themcan be synchronized to the other. The ACU 30 and DCU 34 are also coupleddirectly to the register files 38 so that they can control theiroperation and timing.

With further reference to FIG. 1, the DRAM 44 may also be accessed bythe host 14 directly through a host/memory interface (“HMI”) port 48.The HMI port is adapted to receives a command set that is substantiallysimilar to the command set of a conventional SDRAM except that itincludes signals for performing a “handshaking” function with the host14. These commands include, for example, ACTIVE, PRECHARGE, READ, WRITE,etc. In the embodiment shown in FIG. 1, the HMI port 48 includes a32-bit data bus and a 14-bit address bus, which is capable of addressing16,384 pages of 256 words. The address mapping mode is configurable toallow data to be accessed as 8, 16 or 32 bit words.

In a typical processing task, data read from the DRAM 44 are stored inthe register files 46. The data stored in the register files 46 are thentransferred to the PEs 40 where they become one or more operands forprocessing by the PEs 40. Groups of data bits read from or written toeach set of DRAM columns are processed by respective PEs 40. The dataresulting from the processing are then transferred from the PEs 40 andstored in the register files 46. Finally, the results data stored in theregister files 46 are written to the DRAM 44.

The PEs 40 operate in synchronism with a processor clock signal (notshown in FIG. 1). The number of processor clock cycles required toperform a task will depend upon the nature of the task and the number ofoperands that must be fetched and then stored to complete the task. Inthe embodiment of FIG. 1, DRAM operations, such as writing data to andreading data from the DRAM 44, requires about 16 processor clock cycles.Therefore, for example, if a task requires transferring three operandsinto and of the DRAM 44, the task will require a minimum of 48 cycles.

One embodiment of the command engine unit 20 is shown in FIG. 2. Thecommand engine unit 20 includes a command engine 50 that issues eitherACU commands or DCU commands responsive to task commands received fromthe FIFO buffer 18. The command engine 50 passes ACU commands to the PEFIFO buffer 24 through a multiplexer 52, and DCU commands to the DRAMFIFO buffer 28 through a multiplexer 54. The operations of the FIFObuffers are controlled by a FIFO buffer control unit 56. Themultiplexers 52, 54 also receive inputs directly from the FIFO buffer18. The multiplexers 52, 54 couple the outputs from the command engine50 to the ACU 30 and DCU 34, respectively, in normal operation. However,the multiplexer 52 may couple the host 14 directly to the ACU 30, andthe multiplexer 54 may couple the host 14 directly to the DCU 34 fordiagnostic purposes and, under some circumstances, for programming andcontrolling the ACU 30 and DCU 34.

In the embodiment shown in FIG. 2, the task commands passed to thecommand logic each have 23 bits, and they have the format shown in thefollowing Table 1:

TABLE 1 22 21 20 19 18 17 16 Bits 15-0 Device Select SG WT DeviceSpecific Function Command Data

Bits 22 and 21 identify the task as either a PE task or a DRAM task, theSG bit is a signal flag, the WT bit is a wait flag that is used with thesignal flag SG to perform handshaking functions during the transfer ofdata, bits 18-16 designate the function performed by the task (e.g.,jump, page or data for a PE task or read, write, refresh, etc. for aDRAM task), and bits 15-0 comprise a 16-bit data word that canconstitute an operation code or data that is either operated on or usedto generate an address. In operation, for example, the first task passedto the command logic may designate a specific operation to be performedby the PEs 40 on an operand received from the DRAM 44. The task willinclude device select bits to select either the ACU 30 or the DCU 34,bits 18-16 that indicate a specific function, and bits 15-0 that mayconstitute an operation code corresponding to the specific operation.The wait flag WT may also be set to indicate to the PEs 40 that theyshould not immediately perform the function. The next task may be totransfer the operand from the DRAM 44. In such case, the task commandwill include device bits to select the DCU 34, bits 18-16 that identifya function, and bits 15-0 can provide the address in the DRAM 44 fromwhich the operand is being transferred. The task will also include asignal flag SG that will be coupled from the DCU 34 to the ACU 30 tospecify that the PEs 40 can now perform the specified processingfunction. After the operand has been processed by the PEs 40, theresults data are passed from the PEs 40 back to the DRAM 44 using asimilar handshaking sequence.

The instruction set for the command engine 20 is shown in the followingTable 2:

TABLE 2 Gr. Mnemonic Operation Op code Comment 0 Control InstructionsNOP PC=PC+1 0000 0000 0000 0000 ALERT 0000 0001 0000 0000 Send alert(interrupt) to host. WAITSYS 0000 1111 0000 0000 Wait for data in FIFOand branch. Shifts RL C=U(15),U=(U<<1,C) 0000 0110 0000 0000 Rotate leftthrough carry RR C=U(0),U=(C,U>>1) 0000 0111 0000 0000 Rotate rightthrough carry 0 Bit Operations BITS U=U|(0x8000>>b) 0000 1000 0000 bbbbBit set BITC U=U&~(0x8000>>b) 0000 1001 0000 bbbb Bit clear BITTZ=((U&(0x8000>>b)) 0000 1010 0000 bbbb Bit test => Z ==0 1 RelativeBranch BRR PC=cond?@BRR+3+ 0001 cccc iiii iiii Relative branch cond?@BR#i R+#i 2 Precalculated Branch/Call BR PC=cond?reg 0010 cccc 00rr rrrrPrecalculated cond?reg target in register. CALL PC=cond?reg 0010 cccc10rr rrrr Precalculated cond?reg target in register. 3 Arithmetic andLogical ADD reg U=U+R 0011 m100 00rr rrrr ADDC reg U=U+R+C 0011 m10010rr rrrr SUB reg U=U−R 0011 m101 00rr rrrr SUBC reg U=U−R+C 0011 M10110rr rrrr AND reg U=U&R 0011 m110 00rr rrrr OR reg U=U|R 0011 m110 10rrrrrr XOR reg U=U{circumflex over ( )}R 0011 m111 00rr rrrr <spare> regU=U?R 0011 m111 10rr rrrr 4 Immediate Add ADD #imm U=U+#i 0100 m100 iiiiiiii #i is sign extended to 16 bits 5, 6 Immediates 5 IMME nU=decoded(N) 0101 m100 nnnn nnnn See Table 2-3 for encoding of N 6 IMM kU=(#k,#k) 0110 m100 kkkk kkkk K is copied to both bytes 7, 8, Moves 9 7MOVR reg U=R etc 0111 m10X h1rr rrrr U is modified if u U is 1. LS byteis modified if 1 is 1, MS byte is modified if m is 1. Bytes areexchanged if X is 1. Replaces all MOVR, SWAP and MERGE, MOVRL, MOVRHinstructions. 8 MOVU reg R=U 1000 0000 00rr rrrr MOVPG reg R=PAGE 10000010 00rr rrrr Loads reg with page portion of PC MOVPC reg R=PC 10000011 00rr rrrr Loads reg with @MOVPC+6 STATUS R=[status] 1000 10ss ssrrrrrr Load register from DCU and ACU status. S selects which statusregister. ACU_RESULT R=[ACU result] 1000 11wd 00rr rrrr Load registerfrom ACU Out FIFO. If w is set, instruction will wait until FIFO emptyflag is off before reading the FIFO and continuing execution. If d isset read will be destructive: the next word will be fetched from theFIFO. 9 MOVS reg R U=inF 1001 m1w0 00rr rrrr Load register {u,r2a}directly from in FIFO. U is modified if U is 1. RF reg is modified ifw=1. MOVR_PG NEXT_PAGE=reg 1001 0000 0100 0000 (Mnemonic is MOVU) MOVU_SoutF=U 1001 0000 1000 0000 (Mnemonic is MOVU) MOVR_S outF=R 1001 000011rr rrrr (Mnemonic is reg MOVR) A Skip and SETSn SKIP if (cond) skipnext 1010 cccc 0000 dddd C is condition. instructions D is number ofinstructions to skip−1 SETS Sn = <cond> 1010 cccc ss00 0000 C iscondition. S determines which S flag is loaded (S1 or S2). B- Commands CB DCU_FIFO DCU_FIFO = 1011 ddss wwtt t0000 T: DCU task DCU_OP(s,w,d)Utype: see Table 2-2. D: defer buffer. If 0 task is written immediately.If 1,2,3 command is pushed into the defer buffer of that number. S:Select generation of signal bit (s) in DCU command: S=0 −>s=0; S=1− >s=S1 flag; S=2 −>s=S2 flag; S=3 −>s=1. W: Select generation of waitbit (w) in DCU command: W=0 −>w=0; W=1 −>w=S1; W=2 −>w=S2; W=3 −>w=1. CACU_DATA ACU_InFIFO=R 1100 ff01 00rr rrrr Data read fromACU_InFIFO=Page[R] register file. F: ACU function: 0 - data; 1 -(reserved); 2 - page; (3 - intrinsic call). ACU_TASK ACU_InFIFO=OPCALL1100 11ss wwrr rrrr Intrinsic routine address held in register. S and Wdo the same sa for DCU_FIFO. D Unused, Reserved E Return Stack PUSH andPOP PUSH *(++rsp)<=U 1110 0000 0000 0000 rsp = return stack pointer.Note pre- increment POP U<=*(rso−−) 1110 1000 0000 0000 Note post-decrement. F Memory Operations: multicycle instructions M_LOAD U<=*R1111 0000 00rr rrrr Load U from memory, addressed by register M_LOADPU<=*R++ 1111 0010 00rr rrrr Load U from memory, post- increment addressregister M_LOADN U<=*R−− 1111 0100 00rr rrrr Load U from memory, post-decrement address register M_STORE *R<=U 1111 1000 00rr rrrr Store U inmemory, addressed by register M_STOREP *R++<=U 1111 1010 00rr rrrr StoreU in memory, post- decrement address register. M_STOREN *R==<=U 11111100 00rr rrrr Store U in memory, post- decrement address register.

One embodiment of the command engine 50 that may be used in the commandengine unit 20 is shown in FIG. 3. The task commands are coupled to thecommand engine 50 from the FIFO buffer 18 (FIG. 2) and are applied to aninput FIFO buffer 58. The flag bits 20, 19 and the Device SpecificFunction bits 18-16 are passed to a Cycle, Decode and Microwait ControlUnit 60, which determines the function being performed by the task andcoordinates handshaking using the SG and WT flags. The remaining DeviceSelect bits 22, 21 and the Command Data bits 15-0 are routed to severallocations. The output of the FIFO buffer 58 is coupled to a controlinput of a multiplexer 62. If the Command Data corresponds to aninstruction that the command engine 50 pass data back to the host 14,the multiplexer 62 is enabled to pass the output data to an output FIFObuffer 64. The Cycle, Decode and Microwait Control Unit 60 is alsooperable to stall the operation of the FIFO buffers 58, 62 when they arefull.

If the device specific function bits correspond to a jump in whichinstructions are to be executed starting from a jump address, the jumpaddress is coupled through a first multiplexer 66 and a secondmultiplexer 68 to set a program counter 70 and a delayed program counter72 to the jump address. The jump address is then used to address anInstruction Cache Memory and Controller 76, which outputs an instruction78 stored at the jump address. The Instruction Cache Memory andController 76 is normally loaded by a cache controller (not shown) withinstructions from a program memory (not shown), both of which areincluded in a computer system (not shown) coupled to the active memory10. The Instruction Cache Memory and Controller 76 can be loaded withdifferent sets of instructions depending upon the type of task commandsthat will be passed to the active memory 10.

A portion of the instruction 78 is decoded by a microinstruction decoder80, which outputs a corresponding microinstruction to a microinstructionregister 82. The microinstructions control the internal operation of thecommand engine 50, such as the FIFO buffers, multiplexers, etc. Themicroinstructions are also used to form all or portions of DCU and ACUcommands. The signal paths from the microinstruction register 82 arenumerous, and, in the interest of clarity, have been omitted from FIG.3. The DCU commands and ACU commands are shown in Groups B and C,respectively, of Table 2. The DCU commands shown in Group B includedefer bits “dd” to delay the operation of a command, signal and waitbits “ss” and “ww” bits that are used as described above, and a tasktype “t,” which is normally included in the task received from the host14. The value of the signal and wait bits are stored in respectiveregisters 132, 133. As explained above, the defer values “dd” can bepart of a DCU command, as shown in Table 3.

The DCU commands are shown in Table 3 as follows:

TABLE 3 Bit 20 Bit 19 Bits 18-16 Bits 15-8 Bits 7-0 Flags Function DataSG 0: Null 1: RFA_L Byte count Array RF address 2: Read DRAM Baseaddress 3: Write DRAM Base address 4: Power-up 5: Refresh 6: Sleep 7: LdModeAs shown in Table 3, the DCU commands are Null, Power up, Refresh, Sleepand Load Mode, as well as Read and Write, which are accompanied by aBase address in the DRAM 44, and a register file address (“RFA_(—)1”)command, which is accompanied by the Byte count indicative of the numberof bytes that are to be transferred to or from the register files 46,and an Array RF address, which is the address of the register file to orfrom which the data will be transferred.

The ACU commands shown in Group C include data commands and taskcommands, as shown in Table 4:

TABLE 4 Bits 18-16 Bits 15-0 b20 b19 Function Data Jump SG WT 3 StartAddress of Microroutine Page 0 0 2 (unused) Page address Data 0 0 0 Data

The data command simply includes 16 bits of data, which are transferredfrom the register file 120. Data may also be transferred from the ACU 30to the register file 120 by passing the data designated “acu_ofd”through the multiplexer 124. The task commands include either a jumpaddress or a page address where task instructions are stored.

As mentioned above, the tasks shown in Table 1 that are passed to thecommand generator 50 include 16 command data bits, which may constitutedata that is to be either operated on or used to form an address. In theevent a data word larger than 16 bits is required in an operationcorresponding to an instruction, the instruction may be preceded by animmediate instruction, which are shown in Groups 4-6 of Table 2. Forexample, an Immediate Add instruction shown in Group 4 of Table 2indicates that a data value having more than 16 bits is to be added tothe contents of a U register 96. The immediate instruction is decoded byan immediate instruction decoder 84 and the command data in theinstruction is stored in an IMM register 86. The data stored in the IMMregister 86 is combined with the command data in the subsequentinstruction decoded by the instruction decoder 80 and stored in themicroinstruction register 82. The combined data fields are then passedthrough a multiplexer 88 to an arithmetic and logic unit (“ALU”) 90. TheALU 90 performs an arithmetic or logical operation on the data, andoutputs the results to the U register 96. These operations, and theoperation codes that correspond to them, are shown in group 3 of Table2.

The ALU 90 also provides several conditional values, one of which isselected by a multiplexer 94 for conditional branching of the program.These conditions are shown in Table 5 as follows:

TABLE 5 Code Flag Comment 0 Always Always true 1 C ALU Carry out 2 N ALUresult <0 3 Z ALU result = 0 4 IFE Input FIFO empty 5 S1 Signal/waitflag 1 6 S2 Signal/wait flag 2 7 RFE Result FIFO empty 8 Never Alwaysfalse 9 NC !ALU carry out A NN ALU result >0 B NZ ALU result ! = 0 CNIFE Inut FIFO not empty D NS1 S1 not set E NS2 S2 not set F NRFE ResultFIFO not emptyThe C, N, Z, NC, NN and NZ flags are provided by the ALU 30. Theremaining flags are generated by various conditions that arise in theactive memory device 10, such as the condition of FIFO buffers and bybeing directly set or cleared.

A signal indicative of a branch conditioned on the variable selected bythe multiplexer 94 is coupled to a gate 98, which is enabled by anactive BRANCH microinstruction, to cause the multiplexer 68 to couplethe jump address from the FIFO buffer 54 to the program counters 70, 72,as previously explained. The ALU 90 may also output a return stack ofinstructions to be stored in a U register 96 for subsequently restoringthe program to a location prior to a branch.

Assuming there is no branch to a jump address, the count from theprogram counter 70 is incremented by an adder 100 to provide anincremented instruction count that is stored in a return stack register104 and is coupled through the multiplexers 66, 68 to write theincremented count to the program counter 70. Each command in a routinecorresponding to the task command from the host 14 is thus sequentiallyexecuted. The program count is also coupled to an adder 100 that canalso receive an offset address forming part of the instruction 78. Theadder offsets the program address by a predetermined magnitude togenerate a target address that is stored in a target address register103. This target address is coupled through the multiplexers 66, 68 towrite the target address to the program counter 70. The program counter70 then addresses the Icache memory and controller 76 at a locationcorresponding to the target address.

If the device specific function bits correspond to a page instruction, apage address is coupled through the multiplexers 66, 64 and stored in apage register 106 associated with the program counter 70. Alternatively,if an operation is a deferred operation, the page address is stored in apage register 108 associated with the delay program counter 72. Theaddress space of the ACU can be increased by combining page addressesfrom two page instructions. In such case, a first page address iscoupled though a multiplexer 110 and stored in a next page register 112.The next page address stored in the register 112 can then be combinedwith a page address from a subsequent page command to address a largernumber of ACU program memory addresses storing ACU instructions.

The DCU commands, which include task bits from the instruction 78 aswell as data from the U register, are passed through a DCU FIFO buffer116. The DCU commands can also be stored in multiple defer buffers 118and subsequently passed through the FIFO buffer 116. A dcu_cmd may bedeferred, for example, if an operation must be carried out in the ACU 30or PEs 40 before an operation in the DCU 34 or in the DRAM 44 should becarried out. As explained above, the defer values “dd” can be part of aDCU command as shown in Table 3.

The command engine 50 also includes a register file 120 that isaddressed by a portion of the instructions 78. The register file 120receives write data through a multiplexer 124 from various sources, mostof which have been previously described. In particular the register fileserves as scratch memory for the command generator 50. In addition tothe data previously described, the register file 120 can also store afuture program instruction address by incrementing the current programaddress from the program counter 70 using an adder 126, thereby storinga program address that is two instructions beyond the currentinstruction. Data read from the register file 120 is temporarily storedin an R12 register 128, where it is available at various locations. Forexample, the data from the register 128 may be passed though amultiplexer 130 to an output FIFO buffer 134, which then outputs thedata to the host 14 (FIG. 1). The data from the register 128 is alsoused by the ALU 90 to perform various operations in connection with datafrom the U register 96, as shown in Group 3 of Table 2. The registerfile 120 provides only limited data storage capacity. An SRAM 136 isused to store larger quantities of data, which is transferred to theSRAM 136 from the U register 96. The SRAM 136 is addressed by addressesstored in a memory address register 138.

Although not shown in detail herein, the ACU 30 and the DCU 34 are slaveprocessors that may be similar in structure and function to the commandengine 50. The PEs 40 may be somewhat conventional execution units thatoperate using basic instructions provided by the ACU 30. The DRAM 44 isessentially the same as a conventional DRAM.

A computer system 200 using the active memory device 10 of FIG. 1 isshown in FIG. 4. The computer system 200 includes a processor 202 forperforming various computing functions, such as executing specificsoftware to perform specific calculations or tasks. The processor 202includes a processor bus 204 that normally includes an address bus, acontrol bus, and a data bus. In addition, the computer system 200includes one or more input devices 214, such as a keyboard or a mouse,coupled to the processor 202 through a system controller 210 to allow anoperator to interface with the computer system 200. Typically, thecomputer system 200 also includes one or more output devices 216 coupledto the processor 202 through the system controller 210, such outputdevices typically being a printer or a video terminal. One or more datastorage devices 218 are also typically coupled to the processor 202through the system controller 210 to store data or retrieve data fromexternal storage media (not shown). Examples of typical storage devices218 include hard and floppy disks, tape cassettes, and compact diskread-only memories (CD-ROMs). The processor 202 is also typicallycoupled to a cache memory 226, which is usually static random accessmemory (“SRAM”). The processor 202 is also coupled through the data busof the processor bus 204 to the active memory device 10 so that theprocessor 202 can act as a host 14, as explained above with reference toFIGS. 1 and 2.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A command system fabricated on a semiconductor substrate, the commandsystem comprising: a command engine having an input port structured toreceive task commands from a communications link, and first and secondoutput ports, the command engine being structured to respond to eachreceived task command to output either a processing array command fromthe first port or a memory control unit command from the second port,the command engine being structured to output either the processingarray command from the first port or a memory control unit command fromthe second port based on the nature of the corresponding received taskcommand; an array control unit having an input port coupled to the firstoutput port of the command engine, the array control unit beingstructured to output processing instructions responsive to respectiveprocessing array commands; and a memory control unit having an inputport coupled to the second output port of the command engine, the memorycontrol unit being structured to output memory device commandsresponsive to respective memory control unit commands.
 2. The commandsystem of claim 1 wherein the input port of the array control unit andthe input port of the memory control unit are further coupled to thecommunications link.
 3. The command system of claim 1, furthercomprising a first in, first out buffer having an input port coupled toreceive the task commands and an output port coupled to the input portof the command engine, the first in, first out buffer being operable tostore the task commands at a rate faster than the command engine canoutput respective processing array commands and memory control unitcommands responsive to the respective task commands.
 4. The commandsystem of claim 1 wherein the memory device commands comprise dynamicrandom access memory device commands.
 5. The command system of claim 1further comprising: a first multiplexer having a first input portcoupled to the first output port of the command engine and a secondinput port coupled to the communications link, the first multiplexerfurther having an output port coupled to the input port of the arraycontrol unit; and a second multiplexer having a first input port coupledto the second output port of the command engine and a second input portcoupled to the communications link, the second multiplexer furtherhaving an output port coupled to the input port of the memory controlunit.
 6. The command system of claim 5 wherein the array control unit isstructured to be diagnosed by diagnosis task commands received from thecommunications link through the first multiplexer.
 7. The command systemof claim 5 wherein the array control unit is structured to be programmedresponsive to programming task commands received from the communicationslink through the first multiplexer.
 8. The command system of claim 5wherein the memory control unit is structured to be diagnosed bydiagnosis task commands received from the communications link throughthe second multiplexer.
 9. The command system of claim 5 wherein thememory control unit is structured to be programmed responsive toprogramming task commands received from the communications link throughthe second multiplexer.
 10. The command system of claim 1, furthercomprising a first in, first out buffer having an input port coupled tothe first output port of the command engine and an output port coupledto the array control unit, the buffer being structured to store theprocessing array commands received from the command engine and tosubsequently apply the stored processing array commands to the arraycontrol unit in the order in which the processing array commands arereceived from the command engine.
 11. The command system of claim 1,further comprising a first in, first out buffer having an input portcoupled to the second output port of the command engine and an outputport coupled to the memory control unit, the buffer being structured tostore the memory control unit commands received from the command engineand to subsequently apply the stored memory control unit commands to thememory control unit in the order in which the memory control unitcommands are received from the command engine.
 12. A system, comprising:a host system operable to output task commands; a command engine coupledto receive task commands from the host system, the command engine beingstructured to respond to each received task command to output either aprocessing array command or a memory control unit command; an arraycontrol unit coupled to receive the processing array commands from thecommand engine and being structured to output processing instructionsresponsive to respective processing array commands; a memory controlunit coupled to receive the memory control unit commands from thecommand engine, the memory control unit being structured to outputmemory device commands responsive to respective memory control unitcommands; a plurality of processing elements coupled to receive theprocessing instructions from the array control unit; and a memory devicecoupled to receive the memory device commands from the memory controlunit.
 13. The system of claim 12 wherein the system if furtherstructured to couple the array control unit and the memory control unitdirectly to the host system.
 14. The system of claim 12 wherein the hostsystem comprises a microprocessor.
 15. The system of claim 12 whereineach of the task commands comprises at least one device select bit, thecommand engine being structured to decode the at least one device selectbit in each of the task commands to output either the processing arraycommands or the memory control unit commands responsive to respectivetask commands.
 16. The system of claim 12 wherein each of the taskcommands comprises a plurality of function bits, the command enginebeing structured to decode the function bit and to generate either arespective one of a plurality of different processing array commandscorresponding to respective ones of the decoded function bits or arespective one of a plurality of memory control unit commandcorresponding to respective ones of the decoded function bits.
 17. Thesystem of claim 12 wherein the memory device comprises a dynamic randomaccess memory device.
 18. The system of claim 12 further comprising: afirst multiplexer having a first input port coupled to the commandengine and a second input port coupled to the host system, the firstmultiplexer further having an output port coupled to the array controlunit; and a second multiplexer having a first input port coupled to thecommand engine and a second input port coupled to the host system, thesecond multiplexer further having an output port coupled to the memorycontrol unit.
 19. The system of claim 12 wherein the task commands areat a higher level than the respective processing array commands and therespective memory control unit commands.
 20. The system of claim 12wherein the processing array commands are at a higher level than therespective processing instructions.
 21. The system of claim 12 whereinthe memory control unit commands are at a higher level than therespective memory device commands.
 22. A method of providing processinginstructions to processing elements and memory device commands to amemory device, comprising: receiving a plurality of task commands;determining if each of the task commands is for the processing elementsor for the memory device; if the determination is made that each of thetask commands is for the processing elements, generating at least oneprocessing array command responsive to the task command; if thedetermination is made that each of the task commands is for the memorydevice, generating at least one memory control command responsive to thetask command; generating at least one of a plurality of differentprocessing instructions responsive to respective ones of the processingarray commands; and generating at least one of a plurality of differentmemory device commands responsive to respective ones of the memorycontrol command.
 23. The method of claim 22 wherein the acts ofreceiving a plurality of task commands and determining if each of thetask commands is for the processing elements or for the memory device,comprise: storing the received task commands as they are received; anddetermining if each of the stored task commands is for the processingelements or for the memory device, the determination being made in theorder in which the task commands are received.
 24. The method of claim22, further comprising: generating at least one of a plurality ofdifferent processing instructions responsive to respective task commandswithout receiving corresponding processing array commands; andgenerating at least one of a plurality of memory device commandsresponsive to respective task commands without receiving correspondingmemory control commands.
 25. The method of claim 24 wherein theprocessing instructions generated responsive to respective task commandsare used to perform a diagnosis function.
 26. The method of claim 24wherein the memory device commands generated responsive to respectivetask commands are used to perform a programming function.